1. Field of the Invention
This invention relates to a novel receptor protein which recognizes a cytokine, more particularly, to a novel polypeptide which recognizes interleukin-18 (hereinafter abbreviated as xe2x80x9cIL-18xe2x80x9d).
2. Description of the Prior Art
IL-18 is a type of cytokine or substance which mediates signal transduction in immune system. As seen in Japanese Patent Kokai Nos. 27,189/96 and 193,098/96 and Haruki Okamura et al., Nature, Vol.378, No.6, 552, pp.88-91 (1995), IL-18 was provisionally designated as xe2x80x9cinterferon-gamma inducing factorxe2x80x9d immediately after its discovery: This designation was changed later into xe2x80x9cIL-18xe2x80x9d in accordance with the proposal in Shimpei Ushio et al., The Journal of Immunology, Vol.156, pp.4,274-4,279 (1996). IL-18 in mature form consists of 157 amino acids and possesses properties of inducing in immunocompetent cells the production of interferon-gamma (hereinafter abbreviated as xe2x80x9cIFN-xcex3xe2x80x9d) which is known as useful biologically-active protein, as well as of inducing and enhancing the generation and cytotoxicity of killer cells. Energetic studies are now in progress to develop and realize various uses of IL-18 in pharmaceuticals such as antiviral, antimicrobial, antitumor and anti-immunopathic agents which have been in great expectation because of these properties of IL-18.
As described above, in nature, cytokines including IL-18 are produced and secreted as substances responsible for signal transduction in immune system. Therefore, excessive amounts of cytokines may disturb the equilibria in immune system when they are produced or administered in the body of mammals. The surface of usual mammalian cells may bear certain sites or xe2x80x9creceptorsxe2x80x9d which are responsible for recognition of cytokines: Secreted cytokines transduce no signal in cells till they are bound to the receptors. In normal immune system, there would be definite equilibria between respective cytokines and their receptors. Thus, in this field, with the purpose of developing and realizing IL-18 as pharmaceuticals, in addition to the clarification of physiological activities of IL-18, an expedited establishment of mass production and characterization of IL-18 receptor (hereinafter abbreviated as xe2x80x9cIL-18Rxe2x80x9d) have been in great expectation.
In view of the foregoing, the first object of this invention is to provide a polypeptide as IL-18R which can be easily prepared on a large scale.
The second object of this invention is to provide uses of such polypeptide as pharmaceuticals.
The third object of this invention is to provide a DNA which encodes the polypeptide.
The fourth object of this invention is to provide a process to prepare the polypeptide.
The fifth object of this invention is to provide an agent to neutralize IL-18 using the polypeptide.
The sixth object of this invention is to provide a method to neutralize IL-18 using the polypeptide.
We energetically and extensively screened various means which might attain these objects, eventually resulting in the finding that a substance which recognized IL-18 was present in L428 cell, a type of lymphoblastoid cell derived from a patient with Hodgkin""s disease. We isolated and characterized this substance, revealing that its nature was proteinaceous, as well as that it well recognized and bound IL-18 even when in isolated form. It was also found that the IL-18R thus identified was efficacious in treatment and prevention of various diseases resulting from excessive immunoreaction, such as autoimmune diseases, because in mammals including human, IL-18R recognized and neutralized IL-18 which activated immune system. Further, we have energetically studied L428 cell using as probe some partial amino acid sequences of the IL-18R, resulting in obtainment of a DNA which did encode IL-18R. We confirmed that a polypeptide obtained by bringing such DNAs into expression in artificial manner well recognized IL-18 and shared some essential physiological activities with the IL-18R separated from L428 cell, as well as that it was preparable in desired amounts by recombinant DNA techniques using such DNA. Thus we accomplished this invention.
More particularly, this invention attains the first object with a polypeptide as IL-18R, which is obtainable through gene expression.
This invention attains the second object with an agent for IL-18R susceptive diseases, which contains as effective ingredient such polypeptide.
This invention attains the third object with a DNA which encodes the polypeptide.
This invention attains the forth object with a process to prepare polypeptide, comprising bringing into expression a DNA which encodes the polypeptide, and collecting the resultant polypeptide.
This invention attains the fifth object with an agent to neutralize IL-18, which contains as effective ingredient the polypeptide.
This invention attains the sixth object with a method to neutralize IL-18, characterized by allowing the polypeptide to act on IL-18.
L428 cell, which is feasible in this invention, have been deposited in the Patent Microorganism Depository, National Institute of Bioscience and Human-Technology, Agency of Industrial Science and Technology, 1-3, Higashi 1 chome, Tsukuba-shi, Ibaraki-ken, 305, Japan, under the accession number of xe2x80x9cFERM BP-5777xe2x80x9d on and after Dec. 24th, 1996.